Hygiene refers to the set of activities of daily living and self care skills associated with the preservation of health and healthy living. Hygiene is a concept related to medicine, as well as to personal and professional care practices related to most aspects of living, although it is most often associated with cleanliness and preventative measures. In medicine, hygiene practices are employed to reduce the incidence and spreading of disease. Other uses of the term appear in phrases including: body hygiene, domestic hygiene, dental hygiene, and occupational hygiene, used in connection with public health. The term "hygiene" is derived from Hygeia, the Greek goddess of health, cleanliness and sanitation. Hygiene is also the name of the science that deals with the promotion and preservation of health, also called hygienics. Hygiene practices vary widely, and what is considered acceptable in one culture might not be acceptable in another.

Scrubbing up, hand-washing, especially in an operating room, but in more general health-care settings as well, where diseases can be transmitted[1]

Most of these practices were developed in the 19th century and were well established by the mid-20th century. Some procedures (such as disposal of medical waste) were tightened up as a result of late-20th century disease outbreaks, notably AIDS and Ebola.

Body hygiene pertains to hygiene practices performed by an individual to care for one's bodily health and well being, through cleanliness. Motivations for personal hygiene practice include reduction of personal illness, healing from personal illness, optimal health and sense of well being, social acceptance and prevention of spread of illness to others.

Personal hygiene practices include: seeing a doctor, seeing a dentist, regular washing (bathing or showering) of the body, regular hand washing, brushing and flossing of the teeth, basic manicure and pedicure, feminine hygiene and healthy eating. Personal grooming extends personal hygiene as it pertains to the maintenance of a good personal and public appearance which need not necessarily be hygienic.

The benefits of body hygiene are offset by the risks of excessive body hygiene which is hypothesized to cause allergic disease and bodily irritation. This can be found amongst people suffering from OCD who, for example, can wash their hands excessively.

Some people think that excessive body hygiene can cause allergies. However this is a hypothesis and it is not a proven theory. The hygiene hypothesis states that a marked lack of early childhood exposure to infectious agents, and later a lack of exposure to helminths as adults, increases susceptibility to allergic diseases.[2]. It is postulated that the lack of exposure to these agents prevents the body from developing appropriate allergens and auto-immune responses.

Excessive body hygiene of the ear canals can result in infection or irritation. The ear canals require less body hygiene care than other parts of the body, because they are sensitive, and the body system adequately cares for these parts.[How to reference and link to summary or text] Attempts to clean the ear canals through the removal of earwax can actually reduce ear canal cleanliness by pushing debris and other foreign material into the ear that would otherwise have been removed by the natural movement of ear wax from the interior to exterior of the ear.

Excessive body hygiene of the skin can result in skin irritation. The skin has a natural layer of oil, which protects the skin from drought. When washing, unless using aqueous creams, etc., with compensatory mechanisms, this layer is removed, leaving the skin unprotected.

Excessive application of soaps, creams, and ointments can also adversely affect certain of the body's natural processes. For examples, soaps and ointments can deplete the skin of natural protective oils, and some substances can be absorbed and, even in trace amounts, disturb natural hormonal balances.

Elaborate codes of hygiene can be found in several Hindu texts, such as the Manusmriti and the Vishnu Purana.[3] Bathing is one of the five Nitya karmas (daily duties) in Sikhism, not performing which leads to sin, according to some scriptures. These codes were based on the notion of ritual purity and were not informed by an understanding of the causes of diseases and their means of transmission. However, some of the ritual-purity codes did improve hygiene, from an epidemiological point of view, more or less by accident.

Regular bathing was a hallmark of Roman civilization.[4] Elaborate baths were constructed in urban areas to serve the public, who typically demanded the infrastructure to maintain personal cleanliness. The complexes usually consisted of large, swimming pool-like baths, smaller cold and hot pools, saunas, and spa-like facilities where individuals could be depilated, oiled, and massaged. Water was constantly changed by an aqueduct-fed flow. Bathing outside of urban centers involved smaller, less elaborate bathing facilities, or simply the use of clean bodies of water. Roman cities also had large sewers, such as Rome's Cloaca Maxima, into which public and private latrines drained. Romans didn't have demand-flush toilets but did have some toilets with a continuous flow of water under them. (Similar toilets are seen in Acre Prison in the film Exodus.)

Until the late 19th Century, only the elite in Western cities typically possessed indoor facilities for relieving bodily functions. The poorer majority used communal facilities built above cesspools in backyards and courtyards. This changed after Dr. John Snow discovered that cholera was transmitted by the fecal contamination of water. Though it took decades for his findings to gain wide acceptance, governments and sanitary reformers were eventually convinced of the health benefits of using sewers to keep human waste from contaminating water. This encouraged the widespread adoption of both the flush toilet and the moral imperative that bathrooms should be indoors and as private as possible.[5]

Since the 7th century, Islam has always placed a strong emphasis on hygiene. Other than the need to be ritually clean in time for the daily prayer (Arabic: Salat) through Wudu and Ghusl, there are a large number of other hygiene-related rules governing the lives of Muslims. Other issues include the Islamic dietary laws. In general, the Qur'an advises Muslims to uphold high standards of physical hygiene and to be ritually clean whenever possible.

Bathing did not fall out of fashion in Europe until shortly after the Renaissance, replaced by the heavy use of sweat-bathing and perfume, as it was thought in Europe that water could carry disease into the body through the skin. (Water, in fact, does carry disease, but more often if it is drunk than if one bathes in it; and water only carries disease if it is contaminated by pathogens.) Medieval church authorities believed that public bathing created an environment open to immorality and disease. Roman Catholic Church officials even banned public bathing in an unsuccessful effort to halt syphilis epidemics from sweeping Europe.[10] Modern sanitation was not widely adopted until the 19th and 20th centuries. According to medieval historian Lynn Thorndike, people in Medieval Europe probably bathed more than people did in the 19th century.[11]